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This NOAA satellite image taken Thursday, Jan. 22, 2015 at 12:45 p.m. HARTFORD, Conn. (AP) — A fast-moving coastal storm expected to blast several major cities along the Northeast’s busy Interstate 95 corridor this weekend has begun with sleet and snow.BOSTON (CBS) – It won’t be a blockbuster storm by New England standards, but it WILL be the biggest event of the season thus far for many folks, especially north and west of Boston.

EST, shows a storm system over the Atlantic Ocean with a back-end surface trough that is causing some snow to develop across parts of southern New England. The wintry mix, set to affect more than 6 million people, is due to begin Friday night in areas stretching from West Virginia to New York City, according to Weather.com. The National Weather Service said late Friday that Maryland, Delaware and southern Pennsylvania were experiencing sleet, Washington, D.C., had rain, and West Virginia was getting snow. The temperatures are going to be very marginal at multiple levels of the atmosphere, so a degree or two here or there could mean the difference of several inches of snow versus a mix and rain. A larger developing storm system is located just due northwest of the Gulf of Mexico with a large precipitation shield over most of the Lower Mississippi River Valley.

This swath, including Washington, D.C., and Philadelphia, can expect snowfall until Saturday afternoon, at which point the snow will head north through Boston and up to northern New England. As has been the case with most of our storms so far this winter, there is no real significant source of cold air in place, no cold high pressure anchored in Canada. Today (Saturday): The bulk of this storm is done, but it’s still spinning just off to our east during the early morning, so some impacts are likely to remain.

In and around Pittsburgh, KDKA Meteorologist Jeff Verszyla says we could see between a coating to an inch overnight and into the wee hours of Saturday morning. These slick spots are most likely in our colder suburbs, especially from Loudoun County through the northern half of Montgomery County and to the northwest. However, pockets of iciness are even possible closer to town 11:15 p.m. final update: If you’re longing for snow after all this rain and mixed precipitation, you probably don’t have to wait long.

Tonight’s American models continue to show the likelihood of a strong clipper system dropping a swath of snow across the area starting Sunday night. After a relatively tame start to the winter, Connecticut has plenty of salt and snow-treatment chemicals stockpiled around the state and a fleet of 632 plow trucks ready to go, Department of Transportation spokesman Kevin Nursick said. Winds will begin to veer to a more north-northwest direction, drawing in colder air and changing any rain and mix over to all snow from north to south.

Again, since the strongest winds will be on the backside of the storm they would be out of the north/northwest, generally an offshore direction, other than in Cape Cod Bay. Even those at 32 aren’t generally seeing much if any icing. 7 PM Dulles sounding is isothermal (constant temperature), 1 deg C, in the lowest 8,000 ft.

With surface temps 1-3 deg C above freezing area-wide, and a south wind, it would seem that ice – from here on out – will be a diminishing proposition. Some remain even in NW D.C. several hours after the sleet stopped. 7:45 p.m. update: For the immediate metro area, there are signs the snow and sleet excitement is waning as precipitation shifts to more sleet and rain. Another area of heavier stuff is working its way up from the southwest, and will sweep through in the coming hour or so, perhaps with less snow as temperatures aloft warm. The short range HRRR model shows temperatures aloft below, looking at a current panel and a forecast for 8 p.m. 850 mb (5,000 feet) temperatures are often used as a proxy for simple forecasting of snow vs something else.

Bridges, sidewalks, and some streets may become slippery in places above freezing as well. 5:35 p.m. update: Mixed precipitation has pushed north to the Maryland/Pennsylvania border. Based on reports, the most common type currently falling is sleet, with rain also mixed in to varying degrees for much of the I-95 and southeast area.